1. Field of the Invention
The present invention relates to a method of reusing waste cured resins, in particular, to a method of reusing waste cured resins in which waste cured resins are treated chemically to obtain industrially valuable resin materials.
2. Related Art of the Invention
Cured resins have been widely used in not only coating applications, but also electricity, public works and adhesive applications because of their excellence in physical, chemical and electrical properties.
Thermosetting resins are cross-linked and have a three-dimensional structure when subjected to curing reaction and thereby, in general, become insoluble and non-fusible solid resins. Therefore, cured thermosetting resins are difficult to treat by decomposition, and waste cured thermosetting resins have been regarded as not suitable for reclaiming and reusing and have been disposed of.
However, as more attention has recently been paid to the waste disposal problem, the need has been increased for technological development of reusing and recycling waste cured thermosetting resins, and investigation has been started to thermally decompose the waste cured thermosetting resins and use the same as raw materials. For example, the problem of disposing of waste fiber-reinforced unsaturated polyester resins is serious because a large amount of fiber-reinforced unsaturated polyester resins has been used in manufacturing large-size products such as fishing boats, tanks, and equipment and materials for dwelling.
The problem is, however, that the advantages of cured thermosetting resins themselves, such as hardness, strength, heat resistance, fire retardance and chemical resistance, make it technically difficult to treat their wastes.
Further, thermosetting reins are often used as structural materials due to their magnitude of strength, and there are many cases where such structural materials include metallic materials. Metals are expensive compared with thermosetting resin; accordingly, reclaiming and reusing such materials are considered to be of much importance. For example, copper clad laminates and IC molds using an epoxy resin as a binder include not only paper and fiber, but also noble metals such as copper, gold and silver. In these cases, separation of metals is required as well as reclaiming thermosetting resin.
A method is known in which waste epoxy resins are ground and reused as a filler for molding compounds etc.; however, metals are difficult to separate even with this method, in addition, the fillability of ground epoxy resins are too low to reuse all of them unless they have wider applications.
Recovering and recycling waste cured resins have also been desired strongly from the viewpoint of tight waste disposal places and effective use of resources. It is, however, technically difficult to recycle waste cured resins due to their insoluble and non-fusible properties, and the actual state is that waste cured resins can hardly be recycled with currently used methods.
In light of the above problems, the object of the invention is to provide a method for easily decomposing waste cured resins and separating metals etc. therefrom, and in addition, reusing the same as raw materials.
A method of reclaiming waste cured resins according to the invention is characterized in that the components of a decomposition product produced by bringing waste cured resins, which have at least one type of bond selected from the group consisting of oxazolidone bond, urethane bond, amino bond and ester bond, into contact with a decomposition material which decomposes the above waste cured resins include an alkenyl compound.
In the method of reclaiming waste cured resins according to the invention, preferably the alkenyl compound produced as above and the resin synthesized from the alkenyl compound as a raw material contain 5% or less of the above decomposition material.
A method of reclaiming waste cured resins according to the invention is characterized in that the components of a decomposition product produced by bringing waste cured resins, which have at least one type of bond selected from the group consisting of oxazolidone bond, urethane bond and amino bond, into contact with a decomposition material which decomposes the above waste cured resins include an amino compound.
In the method of reclaiming waste cured resins according to the invention, preferably the amino compound produced as above and the resin synthesized from the amino compound as a raw material contain 5% or less of the above decomposition material.
A method of reclaiming waste cured resins according to the invention includes: a step (A) of bringing waste cured resins, which contain bisphenol A type epoxy resin as a chief material and have at least one type of bond selected from the group consisting of oxazolidone bond, urethane bond, amino bond and ester bond in their crosslinkage, into contact with a decomposition material which decomposes the above waste cured resins; a step (B) of separating and recovering the resin content insoluble in the above decomposition material subsequently after the step (A); a step (C) of subjecting the resin content separated and recovered in the step (B) to a solvolysis reaction with a solvolysis solvent so as to produce glycol or/and glycol ether.
Preferably the above solvolysis solvent is at least one selected from the group consisting of water, methanol, ethanol, ethylene glycol and propylene glycol.
Preferably the above decomposition material is a polycyclic aromatic compound with a boiling point of 200xc2x0 C. or more.
Preferably the above polycyclic aromatic compound is at least one selected from the group consisting of biphenyl, alkylbiphenyl, naphthalene, methylnaphthalene, naphthalenediol, naphthol and naphthoquinone.
Preferably the above decomposition material is a hydrogen donating solvent.
Preferably the above hydrogen donating solvent is tetrahydronaphthalene, for example Tetralin(copyright), available from DuPont.
Preferably the above decomposition material is a carbonyl compound with a boiling point of 100xc2x0 C. or more.
Preferably the above carbonyl compound is at least one selected from the group consisting of methyl isobutyl ketone, isophorone, 2-hexanone, 2-heptanone, 4-heptanone, diisobutyl ketone, acetonylacetone, phorone, cyclohexanone, methylcyclohexanone and acetophenone.
In the method of reclaiming waste cured resins according to the invention, preferably the temperature at which waste cured resins are brought into contact with a decomposition material is 200 to 300xc2x0 C.